bidirectional.md

Bidirectionality

Bidirectionality means that the parsing element of schemas can be run in reverse. This can be really useful for converting back and forth between a "nice" representation and one expected e.g. by an API.

For example, we can create a simple schema to convert a string to and from a date-fns representation.

import { lift } from 'bueno'
import { parseISO, formatISO } from 'date-fns'

const date = lift(
  parseISO, 
  d => formatISO(d, { representation: 'date' })
)

Now, let's say we have a form where we want to edit the following data from our API.

const purchase = {
  currency: '99.00',
  date: '2019-08-11'
}

Our API has stored a currency amount and date as strings, but we'd like to work with this data using real Date and number objects. We simply create the following schema...

import { lift, object, result, toNumber } from 'bueno'

// ...

const schema = object({
  currency: toNumber,
  date: date
})

...parse the data and edit it...

const parsedPurchase = 
  result(schema, purchase)

parsedPurchase.currency = 110.50
parsedPurchase.date = new Date('2020-01-01')

...and we use the schema to convert back to the representation our API expects.

result(parsedPurchase, schema)
// { currency: '110.5', date: '2020-01-01' }

The combinators of bueno will maintain bidirectionality so you can always work with data in the most convenient way without paying the price of manually having to write code converting between various representations.